Propeller control



.lume 28, 1960 D. L. BoGuE PROPELLER comer.

3 Sheets-Sheet 1 Filed Nov. 22, 1957 June 28, 1960 D. L. ABOGUE PROPELLER CONTROL 3 Sheets-Sheet 2 Filed Nov. 22, 1957 INVENTOR. @W2/." gli BY June 28, 1960 File@ Nov. 22, 1957 D. L. BCGUE PROPELLER CONTROL 3 Sheets-Sheet 3 INVENTOR.

PROPELLER CONTROL David L. Bugue, Jupiter, Fla., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 22, 19.57, Ser. No. 698,249'

Claims. (Cl. 170-135.72)

This invention relates primarily to control of aircraft propellers. In modern propeller type power plants including gas turbine engines, it has been found to be highly desirable to use propellers which are capable of pitch varying movement over the entire range from negative pitch, used principally for braking the aircraft, through positive pitch values used normally for propulsion, to a feathered condition. lt is also desirable to provide mechanism which will automatically vary propeller pitch toward the feathered condition in the event of a reversal of power between the engine and propeller. This is provided to prevent high drag on the aircraft resulting from a windm-illing propeller driving the gas turbine engine if the engine should fail for any reason.

Under certain conditions, however, the mechanism which increases pitch in response to a power reversal or negative torque condition may prevent blade pitch reversal. For example, after a plane has touched down in landing with the propeller in a positive blade angle condition, if the pilot operates his control to reverse the propeller pitch, the propeller may run ahead of the engine as the pitch is decreased. If the reverse torque value is high enough to actuate the automatic sensing mechanism, it will signal the propeller to feather and thereby override the pilots demand for reversed pitch. It will be understood that the propeller may not feather fully, but it will increase pitch toward the feathered condition until the torque reversal is terminated. Such partial feather-ing is referred to herein as feathering.

This invention is directed to an improvement in aircraft propeller control systems which eliminates this coniiict and thereby eliminates the possibility that braking by the propeller will be unavailable upon landing the aircraft.

Essentially, the invention comprises means responsive to the control movement by the pilot calling for reverse pitch which disables or inactivates the automatic means which would otherwise increase pitch in response to a reversal of torque.

The nature of the invention and the advantages thereof will be apparent to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings thereof.

Figure l is a schematic drawing of a gas turbine propeller aircraft power plant embodying the control system of the invention.

Figure 2 is a partial view of the front end of the reduction gear of the enm'ne.

Figure 3 is a sectional view of a disabling mechanism taken in a plane substantially perpendicular to the propeller shaft anis.

Figure 4 is a sectional view of the same taken on the plane indicated by the line 4 4 in Figure 3, with parts cut away.

Figure 5 is a detail sectional view taken on the plane indicated by the line 5 5 in Figure 3.

Figure 6 is a sectional view of a portion of the reduction gear assembly, taken on a plane containing the axis Patented .lune 28, 1960 of the propeller shaft, illustrating the mechanism responsive to power reversal.

Referring first to Figure 1, there is illustrated an aircraft power plant comprising a variable pitch propeller P mounted on a reduction gear assembly G driven by gas turbine engine E. The engine is connected to the reduction gear by a shaft housing 10 and two struts 11 as described-in U.S. Patent No. 2,718,756. The engine and propeller are controlled by a pilots power control lever -12 connected by suitable mechanical linkage 13 to the input arm 14 of a coordinating control 16. The eo ordinating control is connected by linkage 17 to an engine: fuel control 18. The coordinating control is also connected by a linkage 19, 21, bellcrank 22 mounted on the reduction gear case, and link 23 to a control input of the propeller. This linkage is illustrated schematically. A linkage of this sort is described in U.S. Patent No. 2,860,712, 1952. The details of the linkage are immaterial to an understanding of the present invention.

The propeller may be of known type, such as that described in U.S. patent application Serial No. 485,921, filed February 3, 1955. The propeller includes mechanism for operation as a speed governing propeller, with blade angle determined by a governor, to hold a set propeller speed and also includes mechanism by which the propeller blades may be varied in direct blade angle control from a negative pitch value through zero pitch and a positive pitch range with blade angle determined by a control input. It also includes mechanism by which the propeller may be feathered. The control mechanism in the propeller may be referred to as pitch varying means. The propeller includes two control rings which are mounted in a non-rotating part of the propeller hub and which are connected to the hydraulic pitch varying means within the rotating part of the propeller. As shown gen-- erally in Figure l, there is a condition control ring 24 having an arm connected to link 23 by which the mode of operation of the propeller, such as positive or negative-y pitch in fixed blade angle control, or speed governing operation, is selected. This condition input is operated directly by the pilots power lever 12 through the coordinating control 16 and the linkage previously described.

The propeller has a second control input ring 26, which may be referred to as the feather input ring. An arm 27 extending from this ring is connected by a link 28 to feathering control mechanism indicated generally as 30 on Figure l. This feathering control mechanism, to be described later, may rotate control ring 26 to cause propeller pitch to increase toward or to the feathered condition.

The link 2S is actuated to cause the propeller to feather by various mechanisms, one of which responds to a power or torque reversal between the propeller and the engine. A mechanism responsive to torque reversal is described in U.S. patent application Serial No. 544,995; The mechanism is illustrated in Figure 6 in suicient detail to explain its relation to the present invention.

Referring to Figure 6, the propeller shaft 32 is mounted in the nose portion 33 of a reduction gear case by bearings Sjfr and 35. The planet carrier 37 rotating with the propeller shaft carries planet gears 33 meshing with a nonrotating ring gear 39. The planet gears are driven by sun gear 4l; on shaft 42. The ring gear 39 is carried by a ring 4.3 which, in turn, is supported in a mounting ring 44 xed in the reduction gear case. The portion 46 of ring 43 is coupled to the fixed support 44 by helical splines 47 which are so pitched that when the propeller tends to overrun the engine, and thus supplies power to the engine through the reduction gear, the ring gear 39 yand ring 46 tend to move forwardly on the splines 47. This forward movement is opposed by a ring of' plungers 48 biased yrearwardly by compression springs 49 which normally hold the ring 46 at its rearward limit of movement. which is sufficient to compress springs 49, the plungers 4S; move forward. When this occurs, one of the plungers` 4S moves a push rod 51 forwardly. Push rod 51 extends through the nose of the reduction gear case and is coupled through mechanism to be described to link 28 and control ring 2o. ,ifhe foregoing description of the torque responsive mechanism is suflicient for anV understanding of the present invention, details thereof immaterial to Y Y the present invention being omitted in the interest of YVa shaft 55. Shaft 5S is mounted in a control assembly housing 57 (see mso Figure 2) bolted to the nose portion 33 ofthe reduction gear case.

If the negative torque exceeds the valuew A bellcrank 58 isY fixed on `the upper endof'shaft 55 which extends lfrom Y the 'housing 57. A forwardly projecting arm of the bellcrank is coupled to Ylink 28 by a commercial ball joint rod end 59.

In the normal operation of the negative torque feathering system,V when the plunger moves forward it acts through member 52 and rocker arm 54 to rotate shaft 'S5 and'pull link 2S to the left, las viewed lin Figure 2. 1 This Iactuates a pitch increasing mechanism `in the prov pellerV which movesV itV tio-ward, the feathered condition.

rl`he member 52 comprises a part` of means for dis- -abling this negative torque signal input to the propeller.,

rPhe pivot pin`53 for member 52 is mounted on a shaft 61, supported by bearings 62 in the housing'57.v YAn arm 63 mounted on shaft 61 may be operated to swing mem?,

ber clockwise, as viewedV in Figure 3, from its normal position in which it transmits movement from push 'rod 51 to rocker arm 54. The member 52 hask a recess 64 cut in the lower portion so thatrthe lower portion 66 Y, of, the outerV end of member 52 Ais of relatively small thickness and the upper portion 67 is of relatively great thicknessl When the member 52. is swung upwardly, plunger '51. may malte its full travel without affecting rocker arm 54, so that no feathering Vsignal is transmitted to the propeller.V

To effect this disabling operation, `arm 63 Yis connectedY Y Vby anadjustable link 63 with ball joint rod ends to anl arm 690i] a rocker shaft '71 rotatably mounted in a supportl Support i2 is mounted on a plate 7'3V bolted to the nose of Vthe reductiongearcase. An arm 74 fixed t Von rocker shaft '71 is coupled by link 76 to the movable member 77 of aV commercial solenoidtyperactuator 78.V

, Y Actuator '78 is energized by leads 80 and 81 from a suit-V able current source, indicatedV in Figure l as suitable source of direct current, through a normally open switch '82 closed bythe pilots power control lever, 12. As indifcated schematically, switch 82 is closed by a cam S3 on lever ,12 which closes the switch whenever the control lever12 is in the range in which the propeller blade Y angle isY fixed, which includes the reverse 'thrustrange In the 'flight range in which the propeller operates under Y control of'a speed governor, switch 82 is open. Thus,

in the ,ightfrange including A'the iiightidle settingA employed du'ing landing'of the airplane, member 52 is VinV l the 'normal position shownfin Figure V3 and the negative VV,torque feathering system is operative. "Whenthe, power control :lever is moved backV into, the fixed blade angie range,fsclenoid '78 is energized to rotate member 52 to the Y, posit-ionwlich disables'the reverse torque feathering system.' i v ,Y n lit-may be also noted, yalthough'it is not of momentV to thepresent inventiomthat propeller control ring 2d may, also beV moved to itsfeat-hering position in response `by including pitch, varying means operable Vto reverse compact. Y Y.

lt' will also be apparent from the foregoing description Y 4 to an electrical signal transmitted tota solenoid actuator 85 mounted on a'bracket 36 fixed to plate 73. The link 87, which is pulled rearwardly by the solenoid 85 when it is energized, is ,connected to one arm of bellerank 55. Thus, when this solenoid is energized, link 28 is pulled to the left, as viewed in Figure 2.V When shaft 5S Vis rotated by push rod 51, the movable part of the solenoid 35 is moved by it. v

The foregoing describes in general the nature and operation of the control systenr of the invention. CertainY features of the preferred structure of the control, as illustrated in Figures 3 to 5, may now be considered. The shaft 55 is mounted in bushings 88 and 89 mounted respectively in the body of housing 57 and in a cover j 55 in the position in which it does not transmit the feathering signal to the propeller. This normal position may be adjusted by la stop screw 97 bearing against end 98 of rocker arm 54. Screw 97, is threaded into housing 57 and bears ya jamb nut 99. Y

Interposer 52 yhasV -a forked end defined by legs 101 which straddle the rear end of shaft 61. Pivot pin 53 passes through bores in the legs 101 and through bushings 102 fitted in a bore in the enlarged end portion 103 of shaft 61. A cross pin 104 pressed into the legs 101 extends with clearance through a slot 106 `in portion 103. A compress-ion spring 108 mounted in aibore 109 in the portion 103 bears against a headed pin 111 which engages, the cross pin1v04. Y Spring 103' exerts a light biasingV force on interposer 52 to hold it in engagement with V[rocher arm 54. Pivot piny 53- is`ret-ainedr1'n place by Figures 3 to 5 Vis particularly well adapted to its purpose.V

Ity is'simple', easyto maintain and adjust, and light and in general of the preferred embodiment ofthe invention thatV the invention provides la simple, and reliable solution to the problem of possible interference between the pilots signal for reverse pitch and the'negative ,torque` responsive VVsystems demand :for movement toward feather-V ing.

The detailed description ofthe preferred embodiment ofV the invention for the purpose of explaining the principles thereof is not to beY construed Vas limiting or -re,

stricting `the Yinventiornias many modifications'r-may be Vmade bythe exercise of skill in the art. i'

YI claim:

Vl. In combination, an engine, la propeller driven therevarying means operable tocause, therpropeller to reverse pitch, automatic feathering control'me'ans, ,interconnecting means connecting the automaticffeathering control means to the pitch kvary'ling' means]operablev by 'the Vautomatic Y Vfeathering control means to cause the propellerto feather, means for disablingY the linterconnecting means, (and means connecting the manually 'operable control meansl to theY u disablingmeans elfective to operate the disabling means Vwhen'the manually operablecontr'ol means is moved'to a position effective to reverse propellerlpitch. 2. In combination, anY engine, a'propeller,drivenftherepropeller pitch and to featherthe'propeller, manually operable control means connectedto the propeller pitch,

engine and propeller, interconnecting means connecting the responsive means to the pitch varying means operable by the responsive means to cause the propeller to feather upon power reversal, means for disabling the interconnecting means, and means connecting the control means to the disabling means eective to operate the disabling means when the control means is moved to a position etective to reverse propeller pitch.

3. In combination, an engine, a propeller driven thereby including pitch varying means operable to reverse propeller pitch and to feather the propeller, manually operable control means connected to the propeller pitch varying means operable to cause the propeller to reverse pitch, automatic feathering control means, interconnecting means connecting the automatic feathering control means to the pitch varying means operable by the automatic featbering control means to cause the propeller to feather comprising a movable input member connected to the automatic feathering control means, an intermediate member, and an output member, the intermediate member being disposed between the input and output members, a control member supporting the intermediate member, a pivotal connection between the control and intermediate members providing for movement of the intermediate member by the input member, means for disabling the interconnecting means comprising means pivotally mounting the control member for rotation about an axis normal to the rst pivotal connection providing for movement of the intermediate member transversely to the direction of reciprocation of the input member, the intermediate member having portions of relatively great and relatively small thickness selectively interposable between the input and output members by transverse movement of the input member, and means connecting the manually operable control means to the control member etective to operate the disabling means when the manually operable control means is moved to a position effective to reverse propeller pitch.

4. A motion-transmitting mechanism including disabling means comprising, in combination, a movable input member, an intermediate member, and an output member, the intermediate member being disposed between the input and output members, a control member supporting the intermediate member, a pivotal connection between the control and intermediate members providing for movement of the intermediate member by the input member, and a pivotal mounting for the control member normal to the rst pivotal connection providing for movement of the intermediate member transversely to the direction of movement of the input member, the intermediate member having portions of relatively great and relatively small thickness selectively interposable between tne input and output members by the said transverse movement of the intermediate member.

5. A motion-transmitting mechanism including disabling means comprising, in combination, a reciprocable input member, an intermediate member, and an output member, the intermediate member being disposed between the input and output members, a control member supporting the intermediate member, a pivotal connection between the control and intermediate members providing for movement of the intermediate member-by the input member, a pivotal mounting for the control member normal to the first pivotal connection providing for movement of the intermediate member transversely to the direction of reciprocation of the input member, the intermediate member having portions of relatively great and relatively small thickness selectively interposable between the input and output members by transverse movement of the intermediate member, and means resiliently biasing the intermediate member against the output member.

References Cited in the le of this patent UNITED STATES PATENTS 

